Unfortunately, mapping neutral hydrogen (H i) gas in emission
from galaxies is difficult at even moderate redshifts
[1]}. This low density
gas imprints, however, absorption lines on the spectra of an unrelated bright
background sources, which offers a powerful tool to study the physical
and chemical properties of the intervening gas in a luminosity independent
manner [2]}. At high
redshift, most of our knowledge of H i  gas primarily comes from a particular class of absorption line systems, the
damped Ly\(\alpha \)  absorbers (DLAs) seen in quasar spectra. With an H i column density of \(\ge 2 \times 10^{20}~\rm cm^{-2}\) , DLAs account for the
bulk (\(> 80\%\) ) of the neutral hydrogen in the early Universe
[3]}, [4]}, [5]}, [6]}.
